The MetService has issued orange-rated strong wind and heavy rain warnings for Otago tomorrow.

The system is forecast to bring heavy rain to the west including the headwaters of the Otago and Canterbury lakes and rives, and severe northwest gales to the south and east.

Heavy rain warnings and watches, also severe gale warnings are in force for many South Island areas.

Heavy Rain Warning / Orange-rated

Area: The headwaters of the Otago lakes and rivers

Period: 13hrs from 5pm Fri, 5 Aug - 6am Sat, 6 Aug

Forecast: Expect 180 to 220 mm of rain about the divide, and 70 to 90 mm within 25 km east of the divide. Peak rates of 15 to 25 mm/h expected about the divide. Note that significant snow melt is likely to occur. Freezing level around 2300 metres.

Strong Wind Warning / Orange-rated

Area: Fiordland, Southland, Stewart Island and Otago

Period: 17hrs from 6am - 11pm Fri, 5 Aug

Forecast: Northwest gales are forecast to be severe at times, with gusts reaching 140 km/h in exposed places.

Strong wind gusts, up to 140kmh in exposed places, could damage trees, powerlines and unsecured structures. Driving may be hazardous especially for high-sided vehicles and motorcycles.

People are advised to keep up to date with the last forecasts in case further watches and warnings are added at MetService.website.